The present invention relates to a power transmission control device, a power transmission device, an electronic instrument, a non-contact power transmission system, and the like.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charging a household appliance (e.g., cordless telephone handset), and the like have been proposed.
JP-A-2006-60909 discloses related-art non-contact power transmission. JP-A-2006-60909 implements data transmission from a power reception device (secondary side) to a power transmission device (primary side) by means of load modulation. The power transmission device detects a change in power-reception-side (secondary-side) load state due to foreign object insertion or data transmission by detecting the induced voltage in a primary coil using a comparator or the like.
According to the technology disclosed in JP-A-2006-60909, the power-reception-side load state is detected by comparing the peak voltage of the induced voltage with a given threshold voltage. However, the threshold voltage used to determine the detected voltage varies due to a change in power supply voltage, a change in distance or positional relationship between the coils, or a variation in an element constant such as a coil inductance. Therefore, it is difficult to appropriately detect the power-reception-side load state.